In the 1938 case Polk Company et al. v. Glover, County Solicitor, et al., the U.S Supreme Court ruled in favor of Polk Company and other plaintiffs who were challenging a Florida law that required out-of-state businesses to pay an annual license tax for selling goods within the state while exempting local companies from this obligation. The court held that this law violated both the Commerce Clause and Equal Protection Clause of the Constitution by discriminating against interstate commerce and treating similarly situated entities differently without a rational basis. This decision reaffirmed principles of economic fairness under federalism, emphasizing that states cannot use their taxing powers to protect local industries at the expense of out-of-state competitors.

In the dissenting opinion for Polk Company et al. v. Glover, County Solicitor, et al., Justice McReynolds argued that the majority's decision to uphold a Florida law requiring citrus fruit dealers to pay an inspection fee was unconstitutional. He believed that this law violated the Commerce Clause of the U.S Constitution by imposing a direct burden on interstate commerce and discriminating against out-of-state businesses in favor of local ones. Furthermore, he contended that it was not within a state's power to regulate or tax products destined for exportation beyond its borders as such actions would interfere with federal authority over foreign and interstate trade. Therefore, according to Justice McReynolds' interpretation of constitutional principles and precedents set by previous court rulings, states should not be allowed to enact laws like Florida’s citrus inspection statute which directly affect interstate commerce.